The Yangtze river dolphin

A now extinct Yangtze river dolphin Photograph: AFP

Researchers take water samples as part of the search for one of the Yangtze river dolphins in November 2006. A team of Sino-international scientists was hoping against formidable, manmade odds that the dolphins would survive Photograph: AFP

Workers clearing floating debris from the surface of the heavily polluted Yangtze river Photograph: Getty

Researchers look through high-powered binoculars in search of dolphins on China's mighty but polluted and traffic-choked Yangtze river in November 2006 Photograph: Peter Parks/AFP

Researchers looking out for the river dolphin Photograph: Peter Parks/AFP

Tomonari Akamatsu, an underwater bio-acoustics expert from Japan's National Research Institute of Fisheries Engineering, uses sophisticated acoustic equipment in search of one of the earth's rarest dolphins Photograph: Peter Parks/AFP

Aquatic research scientist Beat Muller takes a water sample as part of research into the natural habitat of the dolphin Photograph: Peter Parks/AFP

A keeper plays with a finless porpoise, a cousin of the Yangtze dolphin and one of five in Wuhan Baji Aquarium in November 2006. The finless porpoise has proved it can survive and breed in the Yangtze. Nevertheless, because scientists estimate only 2,000 of the small, dark grey mammals survive in the wild, the creature is about to be added to the most endangered species list Photograph: Peter Parks/AFP

Chinese fishermen lift a giant Chinese river sturgeon they caught in the Yangtze river in 2004. The fish, which dates back 140m years, is among the most endangered in China, with fishermen catching as many as 3,000 by mistake every year Photograph: AFP

Endangered Yangtze alligators, bred in captivity, are released back into the wild in Anhui province Photograph: AFP

An endangered giant salamander at the 2005 China International Conservation Festival. The species is threatened by hunting (its flesh is a delicacy), the pet trade and dams Photograph: AFP